Such cables are used in particular for cabling aircraft and spacecraft. They are generally constituted by a conducting core comprising twisted fine strands and insulation constituted by one or more layers of one or more polymer materials. These materials may either be directly extruded over the conducting core or else they may initially be formed into tapes, which tapes are then helically wound around the conducting core. Such insulation is itself frequently coated with a layer of enamel obtained by oven curing a varnish. The insulated conductor or bundle of insulated conductors may be surrounded by an electric screen constituted by wrapped or braided fine strands. The electric screen is itself generally covered with electrical insulation which may be extruded or taped, and which may optionally be coated in enamel.
The insulating polymers and the enamels used are frequently polyimides or fluorine-containing resins or any other material which retains good mechanical properties and electrical insulating properties at operating temperatures of more than about 150.degree. C.
In order to obtain flexible cables and to reduce electrical resistance, it is essential for the metal of the conductors to be suitably annealed. However, when using conductors comprising fine strands having a diameter of less than 0.5 mm, it is known that annealed wires of aluminum or of aluminum alloy are fragile and that they poorly understand the sudden changes in force to which they are subjected during the stranding, insulating, or braiding operations applied thereto, which sudden variations cannot be entirely eliminated in spite of the care taken with said operations of stranding, braiding, wrapping, or insulating. As a result numerous breaks occur in the strands during a manufacturing cycle, which breaks are all the more bothersome since to improve cable flexibility the number of strands is increased while their diameter is reduced.
The object of the present invention is to enable flexible electrical cables to be manufactured comprising strands made of aluminum or aluminum alloy having a diameter of less than 0.5 mm, and which may be as little as about 0.05 mm, while very considerably reducing the risks of breakage during stranding, braiding, wrapping, or insulating operations.